PMID-17978020[0] The Upshot of Up States in the Neocortex: From Slow Oscillations to Memory Formation

slow waves are caused by spreading synchronous up/down depolarizations in the neocortex during SWS

the slow waves are thought to be generated intrinsically (?)

cortex is insensitive in up states, but highly sensitive to thalamic stimulation in down states? humm, need to see the data for that - from slices.

quote: "According to some theories of memory consolidation (Marr, 1971Go; Buzsáki, 1989Go; Squire, 1992Go; McClelland et al., 1995Go), memories are thought to be minted rapidly in the hippocampus during behavior and transferred to the neocortex during slow-wave sleep for long-term storage."

there is other stuff about 50-150 Hz activation in the hippocampus leading to neocortical activation, and that this is associated with transfer from labile hippocampus to long-term neocortex.

the review gives an impression of not being as concrete as, say, Buzsaki.

PMID-17189946[0] Cortico-hippocampal interaction during up-down states and memory consolidation.

(from the associated review) Good pictorial description of how the hippocampus may impinge order upon the cortex:

During sleep the cortex is spontaneously and randomly active. Hippocampal activity is similarly disorganized.

During waking, the mouse/rat moves about in the environment, activating a sequence of place cells. The weights of the associated place cells are modified to reflect this sequence.

When the rat falls back to sleep, the hippocampus is still not random, and replays a compressed copy of the day's events to the cortex, which can then (and with other help, eg. ACh), learn/consolidate it.